RGB LCD Usage Instructions

Introduction

This example demonstrates how to use the GLCDC module of the RA8 series MCU together with RT-Thread’s LCD driver framework on the Titan Board to drive an RGB LCD screen, enabling image display and interface updates. This document provides a detailed overview of RA8 GLCDC peripheral features and the RT-Thread LCD driver framework, along with example configurations and usage methods.

RA8 Series GLCDC Module

1. Overview

The GLCDC (Graphics LCD Controller) is a high-performance graphics controller integrated in RA8 series MCUs, specifically designed to drive TFT/RGB LCD screens. It supports various resolutions, color formats, and graphics processing functions. Combined with RT-Thread’s LCD driver framework, it provides a unified interface for screen initialization, refresh, graphics rendering, and DMA-accelerated operations.

The RA8 GLCDC enables image output from either internal MCU memory or external frame buffers to RGB/LCD displays. Key features include:

Frame buffer control: Supports multiple frame buffers for page switching or double-buffered display
Color format support: RGB565, RGB888, ARGB8888, etc.
Graphics processing: Background layers, text/graphics composition, alpha blending, palette mapping
Synchronization signal generation: HSYNC, VSYNC, DE (Data Enable)
DMA support: High-speed data transfer, reducing CPU load
Interrupt functionality: Frame-end and line-end interrupts

2. Module Architecture

The RA8 GLCDC module mainly consists of the following submodules:

Layer Composition Unit
- Supports multiple layer stacking
- Provides alpha blending, transparency control, and color keying
- Allows rotation and flipping of layers
Frame Buffer Interface
- Supports access to MCU internal SRAM or external memory
- Provides single or double buffering to ensure continuous display
- Works with DMA to automatically read image data
DMA Controller
- Automatically transfers pixel data to the RGB output port
- Configurable burst length to improve bandwidth utilization
- Supports circular transfer, suitable for video or animation scenarios
Timing Generator
- Automatically generates HSYNC, VSYNC, and DE signals
- Supports TTL interface RGB timing
- Polarity, sync width, and front/back porch timings are configurable
Interrupt and Event Controller
- Provides frame-end and line-end interrupts
- Can be used for page switching, dynamic drawing, or scrolling display
- Supports interrupts triggered by DMA transfer completion

3. GLCDC Working Principle

Frame buffer read
- GLCDC uses DMA to fetch image data from memory, supporting single or double buffering for continuous display.
Layer composition
- Supports multiple layers such as background + foreground + icons/text
- Provides alpha blending and palette mapping
Pixel timing output
- Generates HSYNC/VSYNC/DE signals according to LCD interface requirements
- Supports RGB parallel interface, TTL interface, or LVDS (depending on board implementation)
Interrupts and events
- Frame-end interrupt (VBlank): Can be used to update the next frame
- Line-end interrupt: Useful for scrolling displays or dynamic rendering

4. GLCDC Supported Features

Feature Category	Description
Resolution	Up to 800×480 (depending on MCU model and clock)
Color formats	RGB565, RGB888, ARGB8888, etc.
Multi-layer	Background + foreground + icon layers, supports blending
Frame buffer	Single/double buffer mode, DMA improves performance
Palette	8/16-bit palette mapping for color conversion
Sync signals	HSYNC, VSYNC, DE, configurable polarity and timing
DMA support	Automatic memory transfer, CPU-free
Interrupts	Frame-end, line-end interrupts for synchronized refresh
Rotation/Flip	Supports 90°/180°/270° rotation and X/Y flipping

Hardware Description

FSP Configuration

HyperRAM Configuration

Create a r_ospi_b stack：

Configuration r_ospi_b stack：

Configuration HyperRAM pins：

RGB LCD Configuration

Create a r_glcdc stack:

Configure interrupt callback and graph layer 1:

Configure Output、CLUT、TCON and Dithering:

Configure GLCDC pins:

LCD Backlight Configuration

Create a r_gpt stack:

Configure back light PWM output:

D/AVE 2D Configuration

Create a r_drw stack:

RT-Thread Settings Configuration

Enable RGB565 LCD in RT-Thread Settings, using pwm7 output screen backlight.

Example Code Description

int lcd_test(void)
{
    struct drv_lcd_device *lcd;
    struct rt_device_rect_info rect_info;
    rect_info.x = 0;
    rect_info.y = 0;
    rect_info.width = LCD_WIDTH;
    rect_info.height = LCD_HEIGHT;

    lcd = (struct drv_lcd_device *)rt_device_find("lcd");

    for (int i = 0; i < 2; i++)
    {
        /* red */
        for (int i = 0; i < LCD_BUF_SIZE / 2; i++)
        {
            lcd->lcd_info.framebuffer[2 * i] = 0x00;
            lcd->lcd_info.framebuffer[2 * i + 1] = 0xF8;
        }
        LOG_D("red buffer...");
        rt_device_control(&lcd->parent, RTGRAPHIC_CTRL_RECT_UPDATE, &rect_info);
        rt_thread_mdelay(1000);
        /* green */
        for (int i = 0; i < LCD_BUF_SIZE / 2; i++)
        {
            lcd->lcd_info.framebuffer[2 * i] = 0xE0;
            lcd->lcd_info.framebuffer[2 * i + 1] = 0x07;
        }
        LOG_D("green buffer...");
        rt_device_control(&lcd->parent, RTGRAPHIC_CTRL_RECT_UPDATE, &rect_info);
        rt_thread_mdelay(1000);
        /* blue */
        for (int i = 0; i < LCD_BUF_SIZE / 2; i++)
        {
            lcd->lcd_info.framebuffer[2 * i] = 0x1F;
            lcd->lcd_info.framebuffer[2 * i + 1] = 0x00;
        }
        LOG_D("blue buffer...");
        rt_device_control(&lcd->parent, RTGRAPHIC_CTRL_RECT_UPDATE, &rect_info);
        rt_thread_mdelay(1000);
    }
    return RT_EOK;
}
MSH_CMD_EXPORT(lcd_test, lcd test cmd);

Compilation & Download

RT-Thread Studio: In RT-Thread Studio’s package manager, download the Titan Board resource package, create a new project, and compile it.

After compilation, connect the development board’s USB-DBG interface to the PC and download the firmware to the development board.

Run Effect

After reset the development board, type lcd_test command in the terminal to run the brush program.